..Indeed, CD3(-)CD4(-)CD8(-) T-cell-committed precursors can leave the thymus before T-cell receptor rearrangements and then colonize the gut CPs, proceeding with their differentiation within the gut wall...

A role for CD40 expression on CD8+ T cells in the generation of CD8+ T cell memory

..Naive T cells require interactions with the MHC restricting element. The survival requirements of memory T cells are as yet insufficiently characterized, but MHC-restricted interactions are not necessary...

..Both processes depend on the help of CD4(+) T cells, they are irreversible, they have the same mechanism, and they occur progressively during the late expansion phase of the primary immune response...

..Moreover, they belong to the most immature thymocyte population. Collectively, these findings unravel the existence of a postnatal lymphoid-polarized population that is capable of migrating from the BM to the thymus...